For controlling large industrial plants as e.g. gas processing facilities or chemical production plants with hundreds of different devices like electric motors, pumps, reactors, motorized valves, sensors etc., which are hereinafter called control objects, industrial control systems are used. The known industrial control systems usually include electric control systems like field bus systems to which the control objects are electrically connected and over which the data for controlling the control objects as well as sensor data is transmitted to a main computer system. The information about the actual state of the physical control objects like the input flow rate of chemical components which are fed to a chemical reactor or the flow rate and opening positions of control values or the speed and torque of an electric motor, etc. are displayed as stylized objects on large display screens for each control object or for groups of control objects, in order to give the operators an overview of the active state of the process plant. A method and an associated control system of the aforementioned type are disclosed in WO 2001002953A1.
In order to reduce the amount of information displayed on the screen of large process plants, U.S. Pat. No. 8,479,097 B2 suggests a user interface which provides operator screens on which one or more of the stylized objects on the display screen can be selected and grouped by means of a computer mouse. Afterwards, the actual status of the selected group of objects can be displayed as a thumbnail image in a separate window on the same display screen by clicking on an associated tab which is located at the lower end of the display screen. This allows the operator to instantly obtain actual information about process parameters of control objects. According to FIG. 2 of this document, the user interface allows the operator to display alarm or warning messages together with key performance indicators like the main output of the plant, in one thumbnail image, in order to help the operator locate the control objects which have caused the alarm message.